Optimal replacement policies for two-unit machines with running costs: II

In a previous paper [1] we have proved the optimality of a control limit policy for certain two-unit systems with running costs. Under such a policy when either of theunits fails we also replace the other unit if its age exceeds a predetermined control limit. In this work we develop a procedure for computing various important characteristics for any control limit policy including, of course, the optimal one. Some of the resulting characteristics can then be used for a restricted optimization within the class of control limit policies. The fact that this restricted optimization leads to the global optimal is implied by the previous paper. In this sense the two approaches are complementary.